(1) Field of the Invention
This invention relates to a record player and, in particular to a tonearm system for use with a record player providing tangential tracking of the stylus in the groove of the record being played.
(2) Description of the Prior Art
In record players which contain a rotatable turntable for supporting grooved disc records for playing, either of the mono or stereo variety, there is typically provided a tonearm mounted for horizontal swinging movement about a fixed vertical pivot axis, which vertical pivot axis is offset from and is located outside and adjacent to the peripheral rim of the turntable. The stylus of such a tonearm system typically describes an arc as it tracks the record groove, swinging in a generally clockwise direction as the record is played (assuming an outside-in recording).
It is most desirable that tangency be maintained between the tonearm/stylus and the record groove during play, as a lack of tangency gives rise to tracking distortions, and undesirable stylus/groove side pressures generated on the inner side of the stylus because of the frictional force (called "skating force") between the stylus and the walls of the groove of the record.
Any lack of tangency of the stylus with the record groove is undesirable in playing monaural records, but is especially undesirable when playing stereo records containing separate audio channels on opposite sides of the record groove. The reason for this is that not only are distortions introduced, but audio balance is disturbed due to the unbalanced side pressures.
Over the years various means have been provided to achieve tangency between the grooves of a record being played and the central line or axis of the tonearm or pickup and stylus. One means to accomplish this tangential relationship has been to offset the tonearm in which the pickup is supported by a bent arm and to so mount the pickup that it describes an arc across the record. While this maintains relatively good tangency to the groove area over the range of radii covered in modern recordings, it suffers from the disadvantage, (1) that tangency is really only an approximation, and (2) that undesirable side pressures are produced on the stylus so that while the pickup body may be tangential, the stylus itself is pushed out of tangency and the unbalanced forces on the stylus and its supporting mechanism create displacement and distortions which are quite serious.
Another means to accomplish this desired tangential relationship between the stylus and the record groove has been to provide the cartridge itself at an angle to the tonearm. Tonearm systems incorporating such a system are sometimes provided not only with means to adjust the tracking angle, but also means to counter the "skating force", i.e. the inward force during record play which applies lateral forces against the inner groove wall of a record, otherwise desirable minimum record wear and optimum tracking is not achieved.
Straight line motion of the tonearm, or pickup, other than a swinging arc, which tends to assure tangency has been an alternative approach by some in the prior art and various tonearm systems of this type have been provided. An example of such a system is shown in U.S. Pat. No. 2,915,315 wherein there is disclosed a support for a conventional phonographic pickup which is mounted on a moveable carriage and which is driven by an external motor which causes the carriage to maintain the pickup in essentially straight line motion at the stylus tip.
A desire in more recent times is also to make the stylus mass even smaller. Thus, in U.S. Pat. No. 3,356,372 there is disclosed not only a means for moving a stylus in a radial line as a grooved, disc record is being played, but one which is a very small lightweight phonograph pickup having a low friction.
Although some of the prior art systems provide for tangential tracking of a tonearm system in record players and have had some success, these tonearm systems more often have been not only unduly mechanically/electrically complex, but quite expensive. Moreover, they often do not satisfy wholly the requirements of a tangential tracking system, particularly where use of a very low mass tonearm is also desired.